What is the maximum allowed time on a dive to 52 feet after a dive to 72 feet for 30 minutes and a 1:45 surface interval?

To determine the maximum allowed time of a dive to 52 feet following a dive to 72 feet, it is important to consider both the no-decompression limits (NDL) at both depths and the fact that surface interval time can contribute to the overall allowable dive profile.

First, after completing a dive to 72 feet for 30 minutes, you must refer to recreational dive tables or a dive computer to establish the residual nitrogen that remains in your system, which is influenced by the depth and duration of your prior dive. The no-decompression limits indicate the maximum time that a diver can stay at a given depth without needing to perform a decompression stop on ascent. A 1:45 surface interval provides some time for off-gassing, allowing the diver’s body to eliminate some of the nitrogen.

Considering the 1:45 surface interval after a 30-minute dive to 72 feet, this time allows for a reduction in nitrogen saturation. However, when planning the dive to 52 feet, it is essential to reassess the NDL for this new depth taking into account any residual nitrogen from the previous dive.

Typically, divers would find that their allowable time increases with a decrease in depth; however, because of the previous dive,